1. Field of the Invention
The present invention relates to an air data probe for aircraft flight control, and more particularly, to a probe for an aircraft having pneumatic lines that are thermally isolated.
2. Description of Related Art
A variety of air data probe devices are known in the art for aircraft flight control. Of such devices, many are directed to measuring pitot pressure, static pressure, local angle of attack pressures, and angle of sideslip pressures as parameters for calculating pressure altitude, altitude rate, airspeed, Mach number, angle of attack, and angle of sideslip. Air data probes can also provide data for secondary purposes including engine control, artificial feel, cabin pressure differential, and more.
Typically, air data probes include digital and/or analog pressure transducers capable of measuring pressures conducted through pneumatic lines with openings external to the aircraft. This usually involves a pitot-static type probe in which one pneumatic line has an opening that faces into the airflow to measure pitot pressure, and a second pneumatic line that faces orthogonal to the airflow to measure static pressure. Similar pneumatic lines can be employed with openings in various other orientations to measure angle of attack, angle of sideslip, atmospheric conditions, and other metrics.
Many aircraft components are negatively affected by icing conditions, and air data probes are no exception. Icing conditions frequently occur at ground level in cold winter weather. In addition, regardless of the season, the flight envelope of modern aircraft typically includes altitudes where air data probes are subject to sub-freezing temperatures. If there is a sufficient amount of moisture in the air, e.g. when the aircraft enters a cloud, moisture and/or ice can accumulate in the pneumatic lines of an unheated air data probe. The accumulation of moisture and ice within the pneumatic lines of an air data probe can hamper the probe's ability to provide accurate measurements. In a worst-case scenario, the pneumatic lines could become completely blocked with ice, rendering the pneumatic probe incapable of providing useful measurements.
In order to combat the negative affects of accumulated moisture and ice within pneumatic lines, it is known to heat the structures of the probe to drive off moisture and ice. For example, an electrical heating element can be arranged within the interior passage of an air data probe to provide heat sufficient to drive off moisture and ice and keep the pneumatic lines clear.
FIGS. 1a and 1b show a probe 10 that is representative of the prior art. Probe 10 includes strut 20 that has an interior passage 24 accommodating a plurality of pneumatic lines 12, which run from inlet openings in a probe head 22 extending from strut 20. Strut 20 has a baseplate 14, which is attached to a thick faceplate 18, which is in turn attached to the aircraft body 80. Each of the pneumatic lines 12 ends at a respective aperture in baseplate 14. From there, pressure is communicated from the pneumatic lines 12 through a plurality of passages 26 in faceplate 18 into manifold 16. An electrically powered heating element 28 is arranged throughout portions of the interior passage 24 and probe head 22 to allay ice and moisture buildup within pneumatic lines 12.
While probe 10 represents the state of the art, the aircraft skin, faceplate 18, and baseplate 14 can still reach freezing temperatures in some conditions. When these structures reach cold enough temperatures, their large thermal masses can render even state of the art heating element 28 ineffective to heat the portions of the pneumatic paths passing through baseplate 14 and faceplate 18. In severe enough temperatures, heating element 28 can thus be inadequate to prevent buildup of moisture and/or ice within the pneumatic lines. In short, even in the best currently available probes, portions of the pneumatic path can still be subject to ice and/or moisture build up in conditions of extreme cold and moisture.
Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, there remains an ever present need to advance the state of the art for reducing the risk of ice and moisture accumulation in the pneumatic lines of air data probes. There also remains a need in the art for a method and a system that are inexpensive and easy to make and use for reducing ice and moisture formation in the pneumatic lines adjacent to where the probe attaches to the aircraft. The present invention provides a solution for these problems.